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Matchbox Tiger Moth RAAF Air Ambulance


LSP_Kevin

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11 hours ago, LSP_Kevin said:

Thanks again, my dudes. Wasn't able to get much more done today, but I did turn my attention to the canopy once again, as this is the crucial area of this conversion, and the build overall. As you might remember, I've been delaying the decision about opening up the canopy until as late in the process as possible. Opening it up would make it easier to get a good fit, owing to fewer mating surfaces having to match up, but it would also expose the cockpit and hospital stretcher, and also require more detailing work on the opened canopy itself. So the decision was going to hinge (pardon the pun) on which was worse: the fit of the vac canopy (= open it up) or the my work in the cockpit and stretcher area (= leave it closed).

 

In order to arrive at my decision, I had to do some extensive test-fitting and adjustments to the various elements involved, including deepening the ledge at the front of the rear spine, judicious sanding of the vac part, and this:

 

LEARZ8.jpg

 

I carved a recess into the forward fuselage for the new windscreen to sit in, as without it, it would just splay out and look weird. This doesn't exist on the real thing, of course, but was done in the interests of a better result on the model, and shouldn't actually be noticeable in the end. At this point in the proceedings I can say that I'm happy with the cockpit, but not so much the stuff behind it. So the tentative choice at this stage was to keep the canopy closed.

 

Let's do a final test fit after all the adjustments and see what that tells us:

 

k23RCV.jpg

 

Doesn't look too bad! You can see that I've already started to add some internal framing from styrene strip, partly to assist with adding more detail if necessary, and partly to make the canopy more stiff and robust. The clincher, however, is the view from the rear:

 

aZEUUc.jpg

 

There's a fundamental mismatch in the shape of the canopy versus the shape of the resin part where they meet, and I eventually concluded that there was no way of fixing this. If you look carefully, you can also see how dramatically the clear vac part thins from top to bottom, which is why I had to add reinforcing strips to the bottom on each side; on one side, it was so thin it was buckling.

 

So, my final decision is that I really have no option but to open it up! It'll obviate this fit problem at the rear, at least. But another problem lurks, which I'm sure some of you have picked up on already: the clear vac part has the stepped striations from its 3D master evident in its own form, and I don't think anything I can do will make them less noticeable. There's a chance that having the canopy hood open will reduce the visual impact of the issue, but if not, I may have to try to cut the clear panels out and replace them!

 

:blink:

 

Kev


When building vac kits one always hast to match the fuselage to the canopy.  I recommend reshaping (fill and sand) the area behind the canopy to fit the clear plastic.  You may have to blend the change to the area behind it. At the same time continue adding structure to the canopy at its interface the the fuselage. 
 

Unless the lines from the molding pattern are stress lines you have not much to loose by polishing the canopy inside and outside.

 

HTH

Rick

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12 minutes ago, Rick Griewski said:


When building vac kits one always hast to match the fuselage to the canopy.  I recommend reshaping (fill and sand) the area behind the canopy to fit the clear plastic.  You may have to blend the change to the area behind it. At the same time continue adding structure to the canopy at its interface the the fuselage. 
 

Unless the lines from the molding pattern are stress lines you have not much to loose by polishing the canopy inside and outside.

 

HTH

Rick

 

Nah, there's no way I'm going to bother reshaping the spine now. Hinging the canopy hood in the open position solves he problem with a lot less work - and certainly a lot less sanding!

 

And unfortunately in my experience you can't really polish the kind of clear plastic used for vacuforming; in fact, it's even quite difficult to sand. This one certainly has been. But you're right: if I plan to remove the clear panels anyway, then I have nothing to lose by trying to polish them first.

 

Kev

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Nice work so far, Kev! I like your decision to open the canopy, as it would be a shame to hide the stretcher and cockpit details. 
 

As far as the vac canopy, I would do as you are- put some detail inside, give it a dip in Future, and give it a super clean paint job and move on......

 

Keep it up, man!

 

THOR    :ph34r:

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Though I'm not finished yet, I thought I'd pop in and post an interim update on my progress with the canopy. It's been a ton of work so far, and quite a bit more to go yet!

 

You may recall that I had previously been talking about replacing the clear panels between the frames as a way of fixing the visible step marks from the 3D-printed master. After quite an effort to separate the opening section from the fixed section, I quite quickly changed my mind! There's just no way I would have been able to cut out and replace those panels accurately, and in fact it would have been a complete disaster. So, onto Plan B.

 

I did a quick dunk in Future floor polish to see how much things improved, and the result was encouraging. In a previous update, you can see that I had begun work on the internal framing, too. Well, I used Gator's Grip acrylic glue to attach the styrene strip, and when I dunked the canopy in Windex to remove the test coat of Future, it disintegrated the glue, too, and my carefully cut and applied frames fell off! Clearly, I was going to have to start again, using CA this time.

 

Here's a photo of the newly-separated parts, minus the framing:

 

F8aCeD.jpg

 

I had to include a hobby knife in the photo so that the camera had something to focus on! You also get a hint of how buckled and distorted the lower edge of the hood piece is, but here's a close-up:

 

I0YCbA.jpg

 

This is due almost exclusively to the material being paper-thin in this area, and is why I wanted to get those frames on early. You can also clearly see the striations from the master. The circular porthole (also present on the fixed section) is a soft bulge in the plastic, which I'll deal with in due course.

 

So, fast forward a couple of days, and we arrive at this:

 

jfuAyN.jpg

 

It doesn't look like much work, but there were lots of re-dos, changes of plan, fettling and cursing to get this far. The clear panels were sanded and polished as best I could (used the old toothpaste trick on this one), and then the whole thing dunked in Future again. This produced a result orders of magnitude better, though still not perfect. I elected to leave the windscreen quarter panels alone, as I never would have been able to get into that tight space effectively. And yes, I should have done all this as a first step!

 

With regard to the portholes, I punched them out of the canopy parts, punched out clear discs to replace them, and then cut circular vinyl masks on my Silhouette Portrait that overlapped the join (these circular reinforcement plates can be seen in photos of the real thing). Each part was then dipped in Future to seal everything in. It worked great in theory, but unfortunately my execution was a bit off, and the circular masks are not lined up properly with respect to each other, and this will really stand out once things are painted. So, I'm probably going to have to do them again. At least the process is easily reproducible.

 

LcOOxR.jpg

 

And amazingly, the two pieces still fit together!

 

xBh7q5.jpg

 

To finish it off, I need to add the hinge and retraction detail, some cabling, and of course fix my dodgy portholes (misalignment clearly evident in the photo above).

 

Kev

 

 

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8 minutes ago, mozart said:

All your trouble has been worthwhile Kev, the canopy is looking good! I’d have been tempted to try cutting the whole of the aft canopy from 10 thou card with the Silhouette, as I did on my Harvard.......just a thought mebbe? 

 

I thought about doing something like that, but I was worried about matching everything up cleanly, and just decided to go with what I've got.

 

Kev

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Thanks, fellas. I've since fixed the position of the circular reinforcements, though I won't how exact they are until after paint, by which time it's too late! So I'm just going to have to cross my fingers. I'm currently letting another coat of Future cure, before attending to the final detailing.

 

Kev

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